The present invention is directed to a composite filter medium having a pH altering material that allows more efficient capture of microbiological contaminants by the composite filter medium or filtration systems using same.
The present invention is directed to, in a first aspect, a composite filter medium including a positively charged medium comprising: a pH altering material, wherein the pH altering material alters an influent pH such that microbiological contaminants present in an influent maintain a negative charge and the positively charged medium maintains a positive charge and provides enhanced interception of the microbiological contaminants. The pH altering material is adapted to alter the influent pH to less than about 10.5, and more preferably, about 7 to about 9. Preferably, the pH altering material comprises an inorganic carbonate.
The positively charged medium can comprise a solid composite block and the pH altering material is a flat sheet structure wrapped around the positively charged medium. The positively charged medium can also be admixed with the pH altering material and a binder, and extruded to form a solid composite block.
The pH altering material can comprise a flat sheet structure positioned upstream from the positively charged medium. The pH altering material can be periodically regenerated. Composite filter mediums of the present invention may further include an adsorbent for removing charge reducing contaminants upstream from the positively charged medium.
In another aspect, the present invention is directed to a composite filter medium comprising: a charged medium capable of providing enhanced interception of microbiological contaminants; a pH altering layer positioned upstream from the charged medium; and a medium for removing charge reducing contaminants positioned upstream from the charged medium. The charged medium can be admixed with a binder and fused onto a substrate forming a charged layer, wherein the charged layer and the pH altering layer are spiral wound such that the pH altering layer is exposed to the influent prior to the influent contacting the charged layer. The pH altering layer can also be fused to a second surface of the substrate.
In yet another aspect, the present invention is directed to a composite filter medium comprising: active particles treated with a positively charged microbiological interception agent; a binder; a pH altering material, wherein the active particles, the binder, and the pH altering material are admixed and extruded into a solid composite block; and a material for removing charge-reducing contaminants upstream from the solid composite block.
In still yet another aspect, the present invention is directed to a composite filter medium comprising: active particles treated with a positively charged microbiological interception agent; a binder, wherein the active particles, and the binder, are admixed and extruded into a solid composite block; and a pH altering material having a flat sheet structure wrapped around the solid composite block; and a material for removing charge reducing contaminants upstream from the solid composite block. The material for removing charge-reducing contaminants can be incorporated into the flat sheet structure with the pH altering material.
In a further aspect, the present invention is directed to a method of removing microbiological contaminants in a fluid comprising the steps of: altering an influent pH such that microbiological contaminants remain negatively charged by providing a pH altering material upstream from a charged filter medium; and obtaining at least about 4 log reduction of the microbiological contaminants when a fluid is processed through the charged filter medium. The method may further include the step of removing change-reducing contaminants in the influent in coordination with the step of altering the influent pH.
In still a further aspect, the present invention is directed to a filter system comprising: a composite filter medium having a positively charged medium and a pH altering material, wherein the pH altering material sufficiently raises a pH of a fluid processed through the filter system to a pH higher than an isoelectric point of target organisms present in the fluid such that the target organisms assume a negative charge and the positively charged medium maintains a positive charge to provide substantial electric attraction between the target organisms and a surface of the positively charged medium.